In long-distance transmission of optical signals, the accumulation of signal dispersion presents serious problems. These problems intensify with an increase in bit rate and the distance traveled by the optical signals. To date, efforts that compensate for dispersion have mainly involved the use of dispersion compensating fibers, filter-type dispersion compensating devices or a combination of both.
Colorless TODCs have proven quite useful for compensating optical fiber chromatic dispersion. Optical fiber however, imparts not only chromatic dispersion but slope dispersion (change of dispersion from channel to channel of a wavelength-division multiplexed (WDM) optical signal) to optical signals as well. Conventional TODCs exhibit nearly zero dispersion slope, hence they do not provide any significant dispersion slope compensation.